After four years of on-and-off romance, Justin Timberlake and Jessica Biel are finally making it official. But since getting engaged, the couple have been butting heads over the details of their big day.

And there's one demand jealous Jessica just won't drop: No invite for Cameron Diaz.

"Jess considers Cam her love rival," a pal of the couple tells Star. "It burns her up that Justin has stayed friends with Cam after breaking up. When they were going over the invite list, Jess crossed Cam off and told Justin, 'That woman's not coming to my wedding!'"

And Cameron — who split from JT in late 2006 — isn't the only persona non grata at the nuptials. "Jess warned Justin to not even think about inviting another ex, Britney Spears. And she's even limiting Justin's party friends."